Method and apparatus for coating paper



Aug. 24, 1926. r 1,597,218

J. TRAQUAIR METHODAND APPARATUS FOR COATING PAPER Filed July 24, 1922 5Sheets-Sheet 1 IN V EN TOR.

A TTORNEY.

J. TRAQUAIR METHOD AND APPARATUS FOR COATING PAPER Filed July 24, 1922'3 Sheets'Sheet 2 Locus.

m m m w.

A TTORNEY.

Aug. 24 1926.

J. TRAQUAIR METHOD AND APPARATUS FOR COATING PAPER 3 Sheets-Sheet 5Filed July 24, 1922 avg/- e INVENTOR BY r ATTORNEY.

Patented Aug. 24, 1926.

UNITED STATES JOHN TRAQUAIB, OF GHILLIGO THE, OHIO, ABSIGNOB TO THE HEADPULP PAPER 1,597,218 PATENT OFFICE.

COMPANY, 01 DAYTON, OHIO, A CORPORATION 01 OHIO.

METHOD AND APPARATUS FOR COATING PAPEH.

Application filed my 24, 1922. Serial No. 577,692.

My present invention relates to the art of coating paper with a suitablepigment, thereby leveling the surface and filling the pores of thepaper, covering the exposed fibers and providing a good, even surfacefor printing.

- The invention consists in a novel method of coating paper, and inimproved and novel apparatus for putting the method into effect. It isrelated in some respects to the inven- -tion shown in my applicationfiled December 3, 1920, Serial No. 427,934, in that certain featuresthere'disclosed are or may be used in my present invention.

The principal object of my invention is to produce a superior coated paer. Another object is to produce a paper aving all the qualities desiredin coated paper, but having a lighter coat than other high grade coatedpapers heretofore produced. Another object 15 to produce a coated paperwhose surface has less gloss than other coated papers have. Anotherobject is to P ovide means for producing a very high grade coated paperat a cost less than that of producing inferior coated papers by othermethods. Another object is to provide a method by which high classcoated paper, very uniform in quality, may be produced in largequantities. An other object is to provide a method of coating paperwhich will be practically independent of atmospheric or climaticconditions. Other objects, and advantages obtained by my process andapparatus, will appear or be particularly pointed out presentl Iii theaccompanying drawings- Figure 1 is an elevational view of one-half of myimproved coating machine; and

Figure 2 is an elevational view of the other half of the machine. Theright hand end of Figure 2 is supposed to join the lefthand end ofFigure 1. This figure is in reality. substantiall a duplicate of themachine shown in igure 1, and where paper is coated in a manner whichrequires its assage twice through the machine, itpasses directly fromthe machine of Figure 1 to that of Figure 2. Fi res 1 and 2 arediagrammatic to a very arge extent;

Figure 3 is an end view of the troweling mechanism which is shown at Xin Figure 1 and at Y in Figure 2, but in Figure 3 the mechanism isviewed from the opposite side of the machine;

Figure 4 is a view of the troweling machine with the observer facing inthe directionof the arrow in Figure 1;

Figure 5 is a diagrammatic view of a troweling bar, illustrating thetrowelingprocess;

Figure 6 shows an arrangement. for coatmg paper on the second sideimmediately after it has been coated on the first side;

Figure 7 shows a portion of one of the coating units equipped with asingle trowel- 1ng bar. This bar is arranged to oscillate and the figureshows means for oscillating it.

Referring now to Figure 1, it will be seen that paper from the roll Apasses through the coating unit B to the drying unit C. The coating unitcomprises a frame 10, in which rolls 11 and 12 are journaled. Below theroll 11 is a pan or trough 13 containing the coating material. The roll11 dips into the coating material or color, as it is commonly called,and as the paper passes around the roll a layer of color is depositedonv the paper. Coming around to the top of roll 11 the paper passesunder the roll 12, by which the color on the paper is smoothed out and-reduced to the desired thickness, the thickness being varied at will byraising or lowering the roll 12 with the hand wheel 14 and mechanismwhich it is not necessary -to describe. Preferably, one of the rolls hasa hard and the other a soft exterior. The pan 13 may be raised andlowered by mechanism operated with a hand wheel 15 to vary the depth. towhich the roll 11 dips in the color, and when the machine is not inoperation the pan ma be lowered entirely away from the rol". Frombetween the rolls 11 and 12 the paper passes around an idle roll 16,under an idle roll 19, across the troweling device to the drier rolls.

Broadly speaking, that is, in its simplest form, the troweling deviceconsists of a bar 20 having a curved surface which terminates in a sharpedge. The paper is drawn over this curved surface and across the sharpedge at an angle to the locus of the surface at the point where thesurface meets the edge. See Figure 5. The effect of this troweling baris somewhat like that produced by a mason or plasterer when he smoothsthe plaster with his trowel. The plasterer gets the smoothest and mostcompact surface by tilting his trowel slightly and moving it over thesurface of the plaster, at the same time appl mg moderate pressure tothe trowel. I he tilts the trowel too much it will scrape off some" ofthe plaster. But with a very slight tilt, or even with substantially notiltat all, but by making the pressure on the trowel greatest at itsrear edge, .he is able to compact the plaster and im art to it a surfacewhich can'be obtained in no other way. And so it 1s with my trowelingbar; the paper passes over the surface and across the edge, I'OdIICIDmuch the same result thatrthe' p asterer obtains. For this reason, andfor lack of a better term, I have adopted the word troweling to describethe function of the bar 20. Before describin the troweling mechanism inFig I ure 1, I s all explain the steps leading up to the troweling oeration.

I- have employe the term color in referring to the content of the panPreferably, the color consists of a mixture of. water, size and clay. Inplaces I have used the term solution in reference to this mixture,although it is not, strictly s eaking, a.

solution. Instead of clay, satin W ite, blanc fixe, or any other pigmentwhich is ordinarily used in coating paper may be used, and thesemixtures are commonly called color, notwithstanding they may be andusually are white. I use less water than is usual in the color mixture,so little water,

in fact, that the color will scarcely flow.

This results in the layer ofcolor which adheres to the paper as itpassesthrough the pan 13 being thicker than necessary, and the function of theroll 12 is to remove the excess color, so that when finished the coat onthe paper will have a predetermined weight. By the time the paper passesfrom between the rolls the color has become stable. That is, while it isstill wet the color will not'flow on the paper. Two factors contributeto this stability; first the paucity of Water in the. color, and second,absorption of water by the paper. As an aid to this second factor Iprefer to use a soft sized paper, because of its superior absorptivity.Thus, the thickness of the layer of color is kept uniform until itreaches the troweling bar.

When the pa er reaches the troweling bar the color shoul be sufficientlyplastic to enable the troweling operation to smooth the color andcompact it, without removing any of it, and this I refer to as the zoneor point of critical drying. If the color be too dry the action of thebar is insufficient and un-. satisfactory and if the color be too wetthe bar scrapes some of it off. In order to reduce the color tothedesired consistency, I provide for varying the length of time whichelapses between the application of the color to the paper and-itspassage over the troweling bar. This is effected by the moving framewhich carries theidle roll 16 one way or. the other on the brackets 17,thusvarying the distance traversed by the paper before I shall nowdescribe the lural-bar troweling device illustrated in t e drawings, and

refer more particularly to Figures 3 and 4. Extendin from the frame 10of the coating unit are rackets 25, each of which carries bearings,numbered respectively 26 and 27, in which a shaft 28 is mounted torotate. The bearing 26 includes a sleeve 29, within which the shaftrotates, and this sleeve carries a circular disk 30, having an annulargroove or race 31.

sleeve 29 and shaft, making the race eccentrio to the shaft. The sleevemay be rotated to various positions in the bearing 26 by means of a handwheel 32 and fixed in any position with a set screw 33. Keyed The centerof the disk and of the race is offset from the axis of the or otherwisefixed on the shafts are two spiders, 34 and 35, and these spiders act ssupports for the troweling bars 20, the en s of the-bars being turneddown to form spindles adapted to rotate in the holes in the spiders inwhich they are held. In the interest of clarity only two bars are shown,but it is to be understood that there is a circle of bars, as in Figure3. At the ends of the bars adjacent to the disk 30 the spindles 36extend through the spider and carry arms 37, on the free ends of whichare studs 38 arranged to travel in the-race 31. At the other end of theshaft 28 a worm gear 39. driven by mechanism not shown, rotates theshaft and the parts it carries, slowly in clockwise direction as it isseen in Figure 1. I have found three revolutions per minutesatisfactory, but other speeds may be used.

As I have previously stated, in its simlest form the troweling device isa single a'r, as in Figure 5. But I have found in practice thatoccasionally a particle of foreign matter lodges on the edge of the barand marks the coating as the paperpasses over the bar, and the purposeof rotating a plurality of troweling bars in the manner face meets theedge. While the annular race 31 does not maintain the angularity exactly1 of an annular-race, instead of a curve spepaper.

cially desi ned to preserve an invariable angularity, enables me toadjust the relation of the bars to the paper. For example, by rotatingthe disk 30 in the bearing 26 I can change the angularity and by raisingor lowering the idler 19 I can vary the length of the arc of contact ofthe paper. Below the bars I place a pan 49 containing water. Thetroweling bars dip into this water as they move around and by meansof-brushes 41 are washed clean. By this means clean bars areperiodically brought into action to relieve those which have been inaction. Therefore, a particle of foreign matter lodged on a bar couldaffect but a few feet of the paper, which, in view of the rarity of suchan occurrence, is negligible.

In my application previously referred to I described how to adjust theviscosity, that is, the penetrance of the liquid part of the colorsolution to the absorptivity of the To increase the penetrance I addsmall-quantities of silicate of soda if the color be a straight clay,or'gum arabic if the color contains lime, in such a form as satin white,for example. To diminish the penetrance I add a small quantity ofcolloidal size. In my present method this is unnecessary, for in thismethod the weight of the coat on the paper is controlled by raising orlowering the roller, 12, while the consistency of the coat when itreaches the troweling bar is controlled by varying the length of timewhich elapses between the deposit of the color on the paper and itsarrival at the troweling bar. It is quite feasible, however, to utilizethe method of. adjusting'the penetrance of the solution along with themechanical control provided in the present invention. It may be foundadvantageous, for example, to increase the penetrance if hard sizedpaper is being coated, or to reduce the penetrance if the paper is verysoft sized.

My present invention is an improvement over that of my applicationreferred to, among other reasons in thatthe time element here introducedenables me to complete the coating of paper on one side by a single passthrough the machine, involving only one drying of the paper. Sufficientsize may be included in the coating solution to bind the color to thepaper, so that when the paper passes the last drum of the drier'C itneed only be calendered to make it ready for the market. I have hadexcellent success with this one step method, using a solution containing20% of colloidal size. Other sizing materials, such as glue or casein,may be used.

There being so many factors entering into the time element which I havereferred to, it

willbe readily seen that there is no articular time that can beprescribed as t a best. A few figures will not be amiss, however, as anexample. Running the pafper through the machine at the rate of 180 eetper minute with a given color solution I have found that in travelingabout 12 feet the coating attained a very satisfactory consistency fortroweling. But of course this distance may be variedby changing thecharacterof the color solution, or the thickness of the coating, or inother ways. At this rate the elapsed/time is four seconds. I do not wishto be understood to, limit myself to this or any similar time; on thecontrary, one of the articular advantages of my present method, is itsadaptability to various conditions.

The purpose of my double machine, that is, two substantially similarmachines oper ating in tandem, is to coat paper by two stages. One suchuse consists in coating the paper in the first machine with a mixture ofwater, a pigmental material, such as clay, satin white, blanc fixe, orthe like, and a sufficient quantity of size to bind the pigment to thepaper, then passing the paper directly from the drier of the firstmachine to the coating unit of the second machine,

and there giving it a thin waterproof coat-- While not ing comprisingclay and casein.

entirelywaterproof, this coating gives to the paper qualities desirablefor lithographic printing. Another use for the double machine is to coatthe paper first with some pigmental substance suitable for a foundationor filler, and then apply a thin second coat, using a finer quality ofmaterial. By

this means a very fine grade of coated paper may be produced at a lowcost..

'I shall now describe the arrangement of the machines for coating paperon both sides. It will be noticed that the base of unit-D, that is, thecoating unit of Figure 2, is different from that of the coating unit inFigure 1. In Figure 2 the base 50 is mounted upona revoluble sub-base'51, indicated by dotted lines. By means of a pinion 52 emmeshed withteeth on the subbase and turned with a removable crank 53, the sub-basemay be turned so that unit D faces in the opposite direction to that inwhich it faces in Figure 2. In Figure 6 the unit D is shown in thisreversed position. The base 50 is provided with a passage for the paper,and from the drum 54; of the drier C the paper passes through the base,around idlers 55 and 56 and under the roll 11, whereby it is made topass through the color pan 13, between the rolls 11 and 12, around roll16, under roll 19 .and across the troweling bars 20, around idlers 57,58 and 59, to thefirst drum of the drier E. Thus the paper It is notnecessary to describathe calender,

. as it is no different from those well known "by the method I havedescri e very little calendering-is important, In fact,

in the art. -But the fact that a er coated requires so far as the coatedsurface is concerned the window shade. an

pose of removing excess coating an paper might be used withoutcalendering. The-surface produced by the troweling operation is so oodthat it cannot be much improved, an since the uncalendered surface 1sfree from gloss it is desirable to keep it that way. The principaleffect desired from bar brings out these distinctions, but in con-"nection with themethod of coating paper on-the second side immediatelyafter it is coated on the first side, I desire to direct especialattention to one characteristic of the bar. It frequently happens thatthe paper must be" spliced by lapping and pastmgtwo ends of papertogether, and while sucha splice will run over a knife edge withoutdifliculty ifthe paper is lapped so the leading layer is underneath,that is, toward the knife edge, if the paper is lapped the other way,the splice will catch on the knife edge as it goes over and tear thepaper. But where paper is coated on first one side and then the other,as above described, running the paper across the knife edge against thesplice could not be avoided. But the easy approach to theedge of mytroweling bar enables the splice in the paper to run over the bar ineither direction without any danger whatever of tearing the paper.

I have referred to the single trowelin bar as the simplest form of thisdevice, an

in Figure 7, I show an arrangement for troweling the paper with a singlebar. For the purpose of keeping the bar free from partlcles of foreignmatter which might mark the paper I provide means for oscil lating thebar as the paper runs over it. The bar is journaled in brackets whichare attached to the frame 10. and one of these brackets carries abearing for one end of a shaft 71, the other end of the shaft beingcarried by a bearing 72 mounted on the frame 10. Only one of thesebrackets is shown and the vouter extremity of it is broken away toexpose the bar 20. A bevel gear 73 on the end of shaft 71 meshes with agear 74 which is fixed to the end of roll 12. At its other end the shaft71 carries a cam 75. -A square rod 76 is arranged to slidein- 'abearingcarried by the bracket 70, and carries a stud 77 which lies in the camrace 78 and as the shaft 71 rotates the rod 76 reciprocates in itsbearing. An arm with reference to the locus of the paper as it reachesthe, edge, may be varied at will. The oscillation is not required to beat any particular frequency, although I have obtained good results withbar oscillating once for each foot of aper running across the edge. Thelength 0 the movement is not vital, but I have found oscillations ofabout 1 5 of an inch satisfactory. This slight disturbance has theeffect of dislodg ing particles from the bar, and while on thewhole'this al rangement is less effective than the: plural bar scheme,it produces very good results. It is to be understood that the severalrolls of these machines, and other moving parts where it is needed, areproperly connected to rotate and operate in proper relation to oneanother. But these operating connections are not shown, for the reasonthat they do not enter into the invention, and it being well known howto provide such connections they have been omitted, so as to keep thedrawings in simple form, principally diagrammatic.

From the above description it is evident that the relative movement ofthe traveling sheet of paper, and of the troweling device is such that aslippage of the paper with res set to the cooperating device is secured.This relative arrangement is also such that a compacting of the layer-ofcolor is secured along with this relative slippage. The result is theimparting of a smooth surface to the coating of color. Also, the practis--ing of this method permits of greatly reducing the quantity of colorneedful for securing a coating comparable 1n satlsfactorycharacteristics with coated paper made by heretofore practiced methods.

It is to be furthermore understood that the term troweling as usedthroughout the specification is used merely as a brief and apt term fordescribing the particular spreading and smoothing device which isillustrated as a preferred form of the invention; and that this term isnot to be interpreted as limiting the invention to the precise form ofapparatus illustrated. For while I have illustrated and described whatat present I regard as the preferred apparatus for carrying out my newmethod, it is not to be understood that I limit my inventails descrition to the particular apparatus or other deed in this application, asmodifications thereof may be made without departure from the spirit ofmy invention or exceeding the'scope of my claims. What I claim is asfollows:

l. The method of coating aper, which comprises applying a layer of colorto the pa er, and after the color has attained a suitable consistencytroweling the color to compact and make it smooth.

2. The method of coating paper, which comprises applying a. layer ofcolor to the pa er, and after the color has attained a suita leconsistency troweling the color by .drawing it over a surface whichterminates tained a suitable consistency troweling the color "to compactand make it smooth.

4. The method of coating paper, which comprises applying a solution ofcolor to the paper, then after the lapse of suificient time to permitabsorption of water by the paper to reduce the color to asuitableconsistency troweling the color to compact and .make it smooth.

5. The method of coating paper, which comprises passing the paper arounda roll a portion of which is submer ed in a solumake it compact andsmooth.

6. The method of coating paper, which comprises applying a coat of colorof such consistency that it becomes substantially stable as soon. as itis applied to the paper, then after the lapse of suificient time toenable absorption of water by the paper to reduce the coating to asuitable consistency troweling the color to compact and make it smooth.

7. The method of coating paper, whichbeing drawn across said edge at anangle to the locus of said curved surface at the point where the surfaceterminates in the sharp'edge,-the paper being advanced to the trowelingmeans at such a rate'that an interval of time will elapse between theapplication of the color and troweling it, topermit absorption of waterby the paper to reduce the coating to the desired 'consistency fortroweling.

9. In the process of coating paper, wherein the coating'is troweled bydrawing the coated side of the paper over a spreadin and smoothin devicecomprising a plura ity of trowelmg bars brought successively intocompacting and smoothing relation with the coated side of the paper, themethod of preventing injury to the coated surface by the accumulation ofparticles of foreign matte-r upon the successive troweling bars I.

which comprises cleaning each troweling bar after it moves out of oneoperating contact with the coated side of the paper and before it movesinto a succeeding operating contact with the coated side of the paper.

10. The method of coating paper comprising the application of a layer ofcolor contaming so little water that the color is practically stable,troweling the color to .compact and smooth it, and then passing thepaper around a series of drier drums.

11. The method of coating paper comprising the application of a heavylayer of color, removal-of sufiicient color to reduce the coating to apredetermined weight, troweling the color to compact and smooth it afterit has acquired a suitable consistency,

and then passing the paper around a series of drier rolls.

12. The method of coating paper comprising the passage of the paperaround a roll,

a portion of which roll is submerged'in a solution of color, removingexcess color to reduce the coating to a predetermined side of the paper,troweling the color, drying the paper, then immediately applying a coatof color to the other side of the paper, troweling this color, dryingthe paper again, then calendering the aper before rolling it.

14. In a machine for coating paper, aplurality of troweling bars, meansfor moving said bars successively into position which permits of thecoated paper being drawn across them, and means for cleaning the barsafter they have operated on the paper.

15. In a machine for coating paper, a lu- I'ality of troweling barscomprising a sur ace thatterminates in a sharp edge, means for movingsaid bars successively into position which permits of the coated paperbem drawn over said surface and across sai edge at an angle to the locusof the surface at the point where the surface meets said edge,

, and means for rocking said bars on their own coated paper to passacross one or more of said bars, means for causin the active bar or barsto divert the paper rom its path, so that the tension of the paper willcause it to press on the bars as it runs across them, and means forwashing the bars after they have served.

17. In a machine for coating paper, a plurality of troweling barsmounted in revoluble frame, so that the bars lie and move in acylindrical path, each bar havin .a

curved surface terminating in a sharp e ge, means for rotatlng sa dframe, means for passing the coated paper across the bars,

means for causing the active bar or bars to divert the paper from itspath, so that the tension of the paper will cause it to press on thebars, and means for rocking the bars in the frame so that the paper ismade to cross the sharp edge of each bar at substantially the same angleto the locus of its curved surface at the point where it meets the edge,all the while the paper beras on the bar.

18. In a machine for coating paper, a plurality of troweling barsmounted in revoluble frame, so that the bars lie and move in acylindrical oath. each bar havin a curved surface terminating in'asharpe 'ge, means for rotating said frame, means for passing the coatedpaper across the bars,

means for causing the active bar or bars to divert the paper from itspath, so that the tension of the paper will cause it to press on thebars, and a crank on the end of each bar carrying at its'end a stud anda stationar member having a race in which said stu 8 travel as the framerevolves, whereby the bars are rocked in the frame so that the paper ismade to cross the sharp edge of each bar at substantially the same angleto the locus of its curved surface at the point where it meets the edge,all the while the paper bears on theba-r.

1 9. In a machine for coating paper, a plu-- from its path suflicientlyto cause its tension to press it against one or more of the bars,

a pan for containin Xwater into which the lower part of saifgl 'ame,dips and brushes for washing off the bars as they pass through thewater;

20. Amachinefor coating paper comprising a coating uni-t, a'drying unitan a'second coatin unit, arranged in a line in the order name saidsecond coating unit being mounted on a revoluble base, whereby it may berotated through an angle of 180 degrees to cause the unit to face eitherway with reference to the drying unite means for conducting the paperfrom the dryin unit to said second unit, when the latter is in oneposition, so that the paper will be coated again on the same side whichwas coated in the first unit, and means for conducting the paper to thesecond unit when it is in its 7 other position, in such way that the -paer will be coated on the opposite side to t at which was coated in thefirst unit.

21. A paper coating machine comprising two coating units, so positionedwith reference to each other that the paper can pass without stoppingfrom thefirst unit to the second, receiving a coat in each unit; andmeans whereby the paper can be led into the second unit, so it will coatthe sameside of the paper that was coated in the first unit or so theother side will be coated in the second unit.

22. In the preparation of coated paper the method which comprisesapplying alayer of color to the traveling sheet of paper, and vsubjecting the resultant coated paper to a simultaneous smoothing andcompacting action after the paper has traveled a suflicient distancefrom the rolls to insure said smoothin action taking placebeyond thenon-plastic zone of the color.

23. In the preparation of coated paper,

the method which comprises applyin a 1ay-.

er of color to the traveling sheet 0 paper, and subjecting the resultingcoated paper to a spreading and smoothing action at the zoiie ofcritical drying of the said layer of co or.

24. In the preparation of coated paper the method which comprisesapplying a layer of color to the traveling sheet of paper, and passinthe resulting coated paper over a spreading and smoothing member tosecure relative slippage of the coated surface of the paper over thesmoothing and spreading member, while at the same time causing compactinof said coating.

'25. pparatus for coating paper, comprismg means for applying a coatingof color to a traveling sheet of paper; and a smoothing and spreadingmember cooperating with the resulting coated paper and arranged toeffect compacting of the said coating of color,

coated paper and the said-smoothing and so that the traveling sheet ofpaper passes spreading member. thereover to effect slippage of thecoated side 26. Apparatus for coating paper, comprisof the paperrelative to the spreading and 10 I ing mean sio'r applying a layer of athick color smoothing member with concomitant 00msolution to atravelingsheet of paper, and pacting of the layer of color. a spreading andsmoothing member located at the zone of critical drying and positionedJOHN TRAQUAIR. j

